The Problem with Hoard of the Dragon Queen (Spoilers!)
One of the problems of the D&D 5E adventure module Hoard of the Dragon Queen is the goal is too grand at the outset. The adventure is slightly unclear when it should be revealed to the players that the ultimate goal is to stop the dragon cult from raising Tiamat from hell, but it seems to be no later than chapter 3 of the first book when the players are about third level. Yet, the resolution of that goal is not until the end of the second book, Rise of Tiamat, when the PCs are around fifteenth level.
Not knowing that, any reasonable party asks themselves - how do we stop the cult from raising Tiamat? Shockingly the adventure assumes the party will be content to spend the first eight levels of play simply tracking the treasure to find out where it goes and what the cult intends to do with it, but never finding the answer.
It's also unclear whether preventing some amount of treasure from reaching its ultimate destination will slow or stop the cult, or what the PCs could possibly do besides follow the treasure to find out more. It also assumes that the PCs are more motivated to stop the cult than to take a large amount of treasure for themselves and leave.
What I Learned
Running this module taught me a few things about adventure writing and what the word "adventure" should mean.
Most adventures should reach a satisfying conclusion within a few sessions.
Players need to feel a sense of progress. Don't put a goal in front of the players that they cannot do anything meaningful about within a reasonable amount of time. A major milestone or satisfying conclusion should be attainable within a few sessions of play, certainly every character level.
Plot threads should vary in length.
Players should feel natural oscillations between tension and resolution in every session. In addition to 1-2 session adventures, sprinkle in more wandering monsters and random encounters - challenges unrelated to the adventure that can be resolved or circumvented immediately.
I don't mean to fuel edition wars, but when even simple combats started taking 30+ minutes to resolve, we sacrificed wandering monsters and random encounters. We compromised short plot threads and fast oscillations between tension and resolution. When D&D leans heavily into the narrative journey of the heroes, we need to cram the whole Campbellian Monomyth into a reasonable amount of time. The result is we prune anything not immediately pertaining to the main story, and lose all of the shorter plot threads.
What's worse, when we prune the shorter threads and the un-related random encounters, everything feels critically linked to the plot - like the PCs are at the center of a vast conspiracy. That can be fun, but it can also feel like both a quantum ogre and slog. No matter where the PCs go they encounter the main plot and over 15 levels of play every milestone is a baby step in a swamp.
Wait on campaign-level villains.
Don't reveal campaign-level villains or plots too early. In fact, don't even develop them. Many GMs have brilliant, intricate plots fit for an epic fantasy novel. But in an RPG you don't control the protagonists, so you can't control what they're interested in. It's very difficult to keep up the machinations of an ultimate villain in the background of a campaign and the payoff the GM is hoping for ("He was there all along pulling invisible strings and making your lives miserable - the shadow lurking behind every villain you've faced!") is rarely worth the effort.
It's far better to play a sequence of loosely linked adventures and let a grand villain emerge. You could never have foreseen how much the party would despise that NPC, nor how frequently they would reappear and escape again. When your campaign is mature and you're ready for one final adventure, only then do you choose the final dastardly villain.